To provide a system reliability evaluation device for evaluating the reliability of a system in which elements to be required are different for each service and clarifying the elements contributing to the reliability.

The system reliability evaluation device comprises: a fault causing state storage means 16 for inputting the sequence of function sets to the function set of k kinds by increasing functions one by one from the function set of k1 kinds held in a function sequence generation part 31 from the part 31, inputting the result of inspecting whether the system to the function set held in the function sequence generation part 31 is up or down from a system up/down inspection means 15 and outputting the set of states causing a fault; and a system unreliability calculation means 17 for inputting the set of the states causing the fault stored in the storage means 16, the set of the number of fault elements requiring an inspection stored in a means 13 for listing and storing (P+1) pieces of fault states requiring the inspection and a fault probability stored in an element and fault probability storage part 11 and calculating and outputting system unreliability.